1. Technical Field
The invention is related to miniature fiber optic pressure sensors, and more particularly, to catheters with sensors for measuring pressure in the human body.
2. Background
In recent years, optical fibers have formed the basis for many different types of sensors, such as microphones, static and dynamic pressure sensors, strain sensors, among others. Optical fiber sensors can use interferometry or intensity modulation. Intensity modulated fiber optic sensors, while often less sensitive than comparable interferometric sensors, are simpler and less expensive.
The theory of intensity modulated optical fiber sensors, including pressure sensors and microphones, and examples of such sensors, are disclosed in U.S. Pat. No. 7,379,630 to Lagakos et al., U.S. Pat. No. 7,020,354 to Lagakos et al., and U.S. Patent Publication No. 20060072887 to Lagakos et al. The entire disclosure of these documents is incorporated herein by reference. U.S. Pat. No. 7,149,374 to Lagakos et al. discloses fiber optic pressure sensors having an etched diaphragm, and methods for forming the diaphragm. The entire disclosure of this document is incorporated herein by reference.
Optical fibers also form the basis for medical catheter devices for insertion into a human blood vessel. Examples include U.S. Pat. No. 7,447,388, to Bates et al., entitled “Systems and Methods for Minimally-Invasive Optical-Acoustic Imaging” and U.S. Pat. No. 7,396,354 to Rychnovsky et al., entitled “Light Delivery Catheter”, U.S. Pat. No. 7,384,407 to Rodriguez et al., entitled “Small Vessel Ultrasound Catheter” discloses a catheter with a fiber optic temperature sensor suitable for small blood vessels. In “Development of an SU-8 Fabry-Perot blood pressure sensor”, IEEE International Conference on Micro Electro Mechanical Systems, 2005, pp. 810-813, R. Melamud, A. A. Davenport, G. C. Hill, I. H. Chan, F. Declercq, P. G. Hartwell, and B. L. Pruitt disclose a Fabry-Perot interferometer based optical fiber pressure sensor suitable for use in human blood vessels and a method for forming the sensor using photolithography.
M. Shimada, Y. Kinefuchi, and K. Takahashi, “Sleeve-Type Ultra Miniature Optical Fiber Pressure Sensor Fabricated by DRIE”, IEEE Sensors Journal, Vol. 8, No. 7, July 2008, pp. 1337-1341, discloses an interferometric optical fiber pressure sensor and method for forming the sensor.